Sigma’s APO 170-500mm F5-6.3 Telephoto Zoom lens, released over ten years ago in 1993, is getting a new twin sister, the APO 170-500mm F5-6.3 DG. The construction of the two lenses is almost identical, except for the addition of new multi-layer coatings on the DG version to reduce ghosting and flare and create better colour […]